PROJECT SUMMARY/ABSTRACT This proposal presents a 5-year research and career development plan in the study of Mycobacterium tuberculosis. The candidate, Allison Carey, MD, PhD, is currently a clinical fellow in Pathology at the Massachusetts General Hospital who has begun postdoctoral research under the mentorship of Dr. Sarah Fortune at the Harvard T.H. Chan School of Public Health. The proposed career development plan includes a structured training program to provide Dr. Carey with the skills to become an independent investigator at an academic medical center with a research focus on Mycobacterium tuberculosis (Mtb) the causative agent of the globally significant disease, tuberculosis (TB). She will achieve this career goal through the guidance of her mentor, a scientific advisory committee, formal coursework, seminars, and hands-on training in advanced laboratory techniques. Her mentor, Dr. Sarah Fortune, is an established leader in TB research with a history of training successful young scientists, and the members of the scientific advisory committee provide expertise in each facet of the proposed research project. The scientific environment of the Harvard T.H. Chan School of Public Health is exceptionally strong, and is embedded within the greater Boston scientific community, which offers myriad scientific and career development resources. The research proposal builds on the candidate's previous scientific training in classic Drosophila genetics and clinical microbiology, and is focused on the bacterial determinants of Mtb immune evasion. Despite effective antibiotic regimens, the global burden of TB remains high in part due to the failure of prior infection with Mtb or vaccination with Bacille Calmette-Guerin (BCG) to fully protect against subsequent infection or disease, even though a robust immune response is generated. Little is known about the bacterial features that facilitate survival in the face of the pathogen-specific immune response. The candidate's initial post-doctoral work has demonstrated how the genetic diversity that exists among Mtb clinical strains impacts antibiotic susceptibility and the emergence of antibiotic resistance. Here, the candidate seeks to investigate how bacterial features including strain diversity determine outcomes when an immunologically primed host is exposed to Mtb. In Aim 1, comparative genomics and candidate gene approaches will be used to identify bacterial genetic determinants of success during reinfection. Some epidemiologic studies suggest that Mtb strains from the rapidly expanding ?Beijing? sublineage are more likely to escape the immunity provided by BCG vaccination, a hypothesis that will be experimentally tested in Aim 2. In Aim 3, a functional genomics approach, TnSeq, will be used to identify the bacterial genes that are essential for survival and growth in the setting of a primed immune response. The outcome of these aims will answer fundamental questions in the field, inform the development of new therapeutics and vaccines, and open avenues of independent research for the candidate.